Tunable nonlinear optical responses based on host-guest MOF hybrid materials

Abstract

The realization of tunable nonlinear optical (NLO) responses in a single nano-/micro-structure is extremely important. However, in lack of effective ways to integrate multiple performances, it still faces severe limitations during applications. Herein, we demonstrate a wavelength-dependent NLO micro-structure based on host-guest metal-organic framework (MOF) materials through encapsulating linear dye molecules into periodic one-dimensional (1D) channels. The confinement to non-centrosymmetric polar dye molecules enhances the second-/third-order NLO responses of the hybrid crystals, causing obvious two-photon luminescence (TPL), second harmonic generation (SHG) and third harmonic generation (THG) responses in the as-prepared composites. The highly ordered structures of MOFs impart spatial regulation on the linear dye molecules to realize orientation alignment, resulting in the polarized anisotropy emission. NIR-to-NIR (NIR, near-infrared region) two-photon pumped lasing is realized with the natural whispering gallery mode resonance cavities of MOFs under the excitation of a 1200-nm fs laser. Furthermore, tunable NLO properties such as TPL, SHG and THG are achieved through switching the incident excitation wavelength from 800 to 1500 nm. Such hybrid materials with tunable NLO responses may open a new avenue toward designing multifunctional NLO devices in the future.